This invention relates to search and locate systems and, more particularly, to a search and locate system utilizing electrooptic detection means in a manner which facilitates the search and locate process and which provides a high degree of security both for the searcher and for the person being searched for.
Past search and locate systems have been based on the use of omni-directional transmission devices, such as radios, as a locator unit deployed with the person desired to be located. There are several drawbacks inherent in such a system. First, the person desiring to be located has no way of knowing when a searcher is within range of his transmitter and thus, to maximize his chances of rescue, must operate the transmitter for long periods when there are no receivers within range and this is wasteful of the precious power supply available in the locator unit. Further, in a military situation the person desiring to be located, such as a downed pilot, does not want to give his position away to the enemy. Use of a radio transmitter may therefore be highly dangerous in certain situations and in many instances may, in fact, be so dangerous as to preclude use altogether. Also, the use of an active transmitter in the locator unit requires a large power supply and this in turn makes the unit large and cumbersome. Further, omni-directional transmitters are by nature very wasteful of power and very difficult to locate from a single search station such as an aircraft and, at best, can direct the searchers only to a general location rather than to the specific point where the locator unit is positioned.